Olefin and diolefin hydrocarbons are useful for the production of a number of petrochemical products, such as polymers, motor fuel blending additives, and other products. Short chain saturated hydrocarbons having from 2 to 5 carbon atoms per molecule are often subjected to dehydrogenation to form the corresponding olefin. The olefins, in turn, may be used in the alkylation of isoparaffins, in the etherification of alcohols to make motor fuel blending additives, or as monomers used to produce various polymer materials. Olefins can also undergo subsequent dehydrogenation to diolefins.
One particularly useful olefin is propylene, which may be produced by dehydrogenation of propane. Propylene is the world's second largest petrochemical commodity and is used in the production of polypropylene, acrylonitrile, acrylic acid, acrolein, propylene oxide and glycols, plasticizer oxo-alcohols, cumene, isopropyl alcohol and acetone. The growth in propylene production is primarily driven by the industry demand for polypropylene, which is used in such everyday products as packaging materials and outdoor clothing. Other useful olefins include normal butenes, isobutene, and isopentene, which have equally diverse end uses.
One particularly useful diolefin is butadiene, which may be produced by dehydrogenation of n-butene. Butadiene is used primarily as a chemical intermediate and as a monomer in the manufacture of polymers such as synthetic rubbers or elastomers, including styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), polychloroprene (Neoprene) and nitrile rubber (NR). Another useful diolefin is isoprene. The major applications of isoprene include use as a monomer for the manufacture of polyisoprene rubber, styrene-isoprene-styrene block copolymers (SIS) and butyl rubber.
The desired olefin and diolefin products, such as propylene, isobutene, normal butenes, butadiene, isopentene and isoprene are generally produced in separate, non-integrated, systems, one system producing propylene from propane, one system for producing isobutene from isobutane, a third system for producing normal butenes and/or butadiene from n-butane (or butadiene from n-butenes), and a fourth system for producing isopentene and/or isoprene from isopentane. While it has been proposed to co-process propane, isobutane, and n-butane feeds simultaneously in a single reactor, reactor performance generally declines when the feeds are combined and processed together. This is because reaction conditions (temperature, pressure, space velocity, etc.) can only be selected to optimize the relationship among selectivity, conversion, and energy consumption for one of the products and, therefore, the other product or products are produced at non-optimal conditions.